Induction-motor.



R. B. HELLMUND.

INDUCTION' MOTOR.

APPLICATION FILED 1111112211901.

1,011,783. Patented 1160.121911.

UFF 1y 11 Kamm fly J R. E. HBLLMUND.

INDUCTION MOTOR.

APPLICATION FILED JUNE 22. 1007.

1,01 1,783. Patented B90111911.

7 SHEETS-SHEET 3.

R. E. HELLMUND.

INDUCTION MOTOR.

`APPLICATION FILED JUNE 22. 1907.

1,011,783. Patented Dec. 12,1911.

7 SHEETS-SHEET 4.

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@@@Wf fflfdfmm H. E. HELLIVIUNL NDUGTION MGTOR.

AMLIGATION NLM mmm,

. v Patented Dec. 12,1913.,

TSKBETS-SHE @need RUDOLF E. HEILMUND, OF HINSDALE, ILLINOIS, ASSIGNOR,BY MESNE ASSIGNMENTS,

TO GENERAL ELECTRIC COMPANY, A VCORI-ORATION OF NEW YORK.

iNDUcTIoN-Moron.

Specication of Letters Patenti.

Patented Dec. 12, 1911.

Application filed June 22, 1907. Serial No. .380,349.

To all whom 'n may concern:

Beit known that I, RUDOLF EL IIELLMUND. citizen of the United States,residing at Hinsdale, in the county of Dupa ge and State of Illinois,have invented a certain new and useful Improvement in Inductioil-Motors,of which the following is a full, clear, concise, and exact description.

My invention relates to induction motors, and its object is to providemeans for controllingthe operation of variable speed motors of thistype.

My invention contemplates an induction motor having two or more sets ofwindings', so' as to produce different numbers of poles, in combinationwith switching means adapted to bring theA different sets of windings"successively into circuit. This gives the rotor a speed correspondingtov whichever of the windings is energized. y

l One feature of my invention consists in locating the electricallyindependent windings in the same stator slots, each winding, however,embracing a diierentnumber of slots to produce the different numbers ofrotating'magnetic poles. The high speed windings are preferablylocatedjin the bottom of the slots, with the low'speed windings at thetop, since the tendency of magnetic leakage from the low speed windingsisy decreased by reason of. their location in proximity to the rotor.

A lfurther feature of my invention consists in an arrangement whereby,in starting, the low speed winding is switched into serv\ ice .beforethe high speed winding, thereby obtaining favorable starting conditions.

A 'further feature consists in an arrangement for controlling thecurrent tothe motor windingsin such manner that in stopping the motorthe windings are brought into circuit in successive order from theV highspeed downto the low speed. In this arrangexnentthe switching of the lowspeed winding into service causes a braking effect by reason of therunning of the rotorata speed above the normal low speed The motorrunning'abovesynchromsm acts as a generator, fand currentiis" returnedto. the

main circuit, preferablythroughan anto-` transformer, which stepsfup thevoltagev so that the return currentgis'fnpt excessive. The

advantage of-this' "isthatitprevents undue variations inthe averagecurrent in the main circuit.;

A further feature of my invention consists in means for overcoming theremaining inertia produced by the low speed winding, in stopping themotor. This may be done by momentarily reversing one of the phases ofthe low speed winding. For this latter purpose an automatic controllerswitch is provided, having means, such as a pendulum, to swing thecontroller momentarily to the reverse position in stopping, so as toproduce increased braking torque between the low speed and zero.

V'These and other features of my'invention may be more readilyunderstood by reference to the accompanying drawings, in which- Figurel' is a diagram of a circuit for a two phase, two speed motor; Fig. 2 isa similar diagram. of a motor adapted to rotate inv either direction;Fig. 8 is a diagram of the circuit arrangement of a two p hase, two

speed motor with an autotransformer; Fig..

4 is a diagram similar to that shown in Fig. 3, but in which the motorin stopping is switched directly from full voltage high speed winding tothe low speed Winding atpartlal voltage; Fig. 5 is a diagramcorrespending to Fig. 3, for a three phase, three speed motor; Fig. 6 isa diagram of a two speed, three phase motor in which the movablecontacts are electrically connected to the mains; Fig. 7 is a diagram ofthe stator of two phase motor wound toproduce 6 and 12 polesrespectively; Fig. 8 shows the Y characteristic curve of the current fora three speed motor without an autostarter; Fig. 9 is a diagram showingthe torque corresponding to the current illustrated in Fig. 8; Fig.A 10is a diagram of a star wheel used in connecin Fig. 4; Fig. l1 is a sideelevation, w'th aA portion of the cover removed, of the sw ,tch-

tion with the circuit arrangement illustiated ing mechanism forming partof my inten-lv tion.'and especially adapted for use in donnection withthe circuit arrangement shown,

sent the high and low speedwindings. re-

spectively, and in Fig. 5, which shows 'a three speed motor, Irepresents c wlndmg for pro- Aducing a' speed intermediate the other.two

respectively, are connected to the low speed winding L'. Byra stillfurther movement of contacts a, a1, the fixed contacts b and c2 and 1ande3 are bridged soas to switch in the high speed 'winding II. Fig. 2illustrates substantially the .same manner of connecting the mains tothe high and low speed windings, said .gure also showing means for reversing the direction of rotation by moving the movable contacts a al,to the left of their' normal or o position.

'Fig'. 3 illustrates an autotrausformer T employed in connection withmyinvention.r

With such arrangement, when the movable contacts a, 0.1, t, t, are movedto position I, phases A and B are connected to the low speed winding Lthrough the autotransformer T withl only part voltage of the` mains.lVhen said movable contacts are in position IIthe low speed windingsreceive full voltage of the line; -in position III the high speedwindings H are switched in circuit through the'transformer, receivingonl f part voltage; and in position IV said `hig speed windingsre'ceivefull voltage ofthe line. It will be observed that in all operatingposit-ions the autotransformer is bridged across the line, for reasonshereinafter described.

Fig.' l shows an arrangement similar to that shown in Fig. 3, exceptthat intermediate positions II and Ill, an additional position IIa isprovided. In the forward movement, in bringing the motor up to speed themovable contacts do not rest in position IP. -IIowevenin the reversemovement to stop the motor, said contacts movi` from position IV to IIandtrom II to ott1 position. In position IIn the` low speed windings Lare in circuit with only partial Avoltage of the line.- This change fromhigh speed with full voltage to'low speed with partial voltage causesthe motor to run above synehronism, said motor thereby acting as agenera-tor and returning current through the transformer T to the maincircuit. As before stated, the advantage of this is thatit preventsundue variation in the average' Acurrent in the main circuit.`

l In Fig. 10 I havev illustrated a star wheel particularlyadaptedgforjuse in connection with the structure illustrated in Fig. 4.As shown therein the periphery of the star wheel s issuch that theroller 1' in the forward movement of the wheel rides over the elevationsepa-rating positions IIl and III, but 1n the return movement 1s adaptedto through w ping at the latter position only.

Fig. 5 is a; diagram so newhat similar to that shown in Fig. .britillust-rating low, intermediate and highffsoeed windings.L, I

ride out of all positions and H, respectively; in lconnection witli'athree phase system.

Fig. 6 illustrates an arrangement similar to that shown' in Fig. 2,butvrditlering there from in that the mains are shown as electricallyconnected to movable contacts al. au

a three phase current is employed. 'z

Referring to I 1g. I have illustrated as t-yliical of the system ofwinding which -torms a feature ot my invent-ion, 'a stator for atwo'phase system having two 'sets windings adapted to produce six ortwelve poles, according to which set otwindings are energized. The lowspeed windings L are shown in the diagram in position'to indicate theirlocation in the top part. of the usual slot. since thereis a: greatertendency of magnetic leakage from the low 'than from the high speedwinding, and this arrangement, as hereinhefore stated, tendsto overcomethis magnetic leakage.

The motor may be braked, ashereinbefore stated, by momentarily reversingthe motor. Mechanism for automatically accomplishing this purpose isshown in Figs. 11', 12 and 13, said figures showing a. controllerespecially' applicable to the circuit arrangement'shown in Fig. 6. The'movable contacts (l are carried by a. wooden controller drum B, havingpivot extensions 79, provided with suit able bearings in te frame F.The. engagement of said movable contacts with the fixed contacts eandel, respectively, control the forward and reverse connection of thelow speed windings to the mains. Iiikewisecontacts e, c, control theflow of current through the high speed windings. The drum may beoperated in any well known manner, as for'exaniple, by means of anelectric dynamometer or motor having an armature N and a field magnet M,as clearly seen in Figs. l2 and 13 o the drawing. The armature and tieldwindings of the motor are connected upin the. well known manner.Movingwith `the controller drum is s. pendulum like weight P which 'actsas acounter-V torque .tor the motor. The greater the current. suppliedthe armature of the motor the greater the torque develo d by it, andcon- :120

sequ'ent'ly the greater 't e' angle through which it moves; By varying.the amount df current su plied the armature N, the angle hlchit movesmaybe varied, and by `varying* the direction 'of flow through thearmature N, thedirectionl in which'it moves may be reversed so that anyof the stationary contacten, c, e,' or e may be engaged by the movablecontacts (l. The *n-' .ertia of-said weight P swings the controllermomentarily to the reverse position in stopcurrent, will ping. `Forexample, if the lmovablegcontacts fl arc in engagement with the fixedcontacts e and the drum B is released, the weight P causes 'said movablecontacts to momentarily engage contacts e1, thus reversin the 'cur rentthrough the low speed win ings and causing the braking torque.

The startin torque, as well as the starting practically constant duringthe periods of starting. These conditions are illustrated in Figs. S and9, which' show in heavy lines the characteristic curves for the "currentand the torque, respectively, where windings for three speedsA areemployed without an autostarter.' It will be noted that in starting, bypassing successively from the low through' the intermediate to the highspeed windings, the starting torque is high, while the current iscomparatively low, and both the'current andthe torque are practicallyconstant,v thus providing the most favorable,"starting conditions. Thelower l 'curve in Fig. 8 indicates the current given -to the vvlineWhile passing in a reverse direction from the hi h to thel low speedwinding.v Likewise tr e heavy curve below the line inFig. 9'indicatesthe braking or countertorque obtained vin stoppingand the g the brakingtorque obtained if the reversing scheine shown in Fig. 6,"fory example,be employed. A

",Thcfrotor forming a part o'l niy inotor 4may beof the 4usualsquirrel-cage type, and hencefa description and showing ot the saine isunnecessary. Y

My invent-ion provides u. variable speed inotor, since a speed ofrotation can be obtained corresponding to the winding eneigizcd.Furthermore, as before stated, when yt. is desired to stop the niotor,the windings are brought. into circuit in .successive order 'from thehigh speed down to the low speed. As a result the rotor is electricallybraked within itself by'incansof the back torque on the rotor. This isdue to the tact; that when the winding which gives thtl rotor the speedat which it is running is cut. out. and the winding for the neLyt speedis cut in, the rotor will be ruiming :it a speedwhich isI)vcr-synchronous .with respect. to this latter winding, andconsequently a braking action will take place until the speedotthc rotorhas fallen to a speed corresponding to the latter winding. Thisoperation takes place at'cach stepuntil the low speed winding has beenreached, and the rotor will then have only asmall proportion of theinertia it had when running at the higher '.speed. This remaining'inertia maybe .overcome in 4cessive order from low .speedto. high speedeither of the two ways hereinbefore de-` 6U- scribed. i

With the motor of my invention, the fol!" lowing advantages may beobtained: variable speed; considerable improvement in the startingconditions; Very effective electric braking down to low speed andeiicicnt braking down to zero; and high etliciency for-all speeds.'AHaving described my invention, I claiin: l. Inra control system for analternating curient motor, the combination with a pluralit-y of sets ofwindings for producing different speeds, of a controller adapted toconnect said sets of windings in circuit in siicto start said motor andto cnt said sets of windings out of circuit in successive order fromhigh-speed to low speed to stop said motor, and means carricd'by saidcontroller adapted tol cause said .controller to. connect in circuit thelow speed winding in one direction after all of the windings in the upfpositc direction have been cut out ot'cireuit `trom high speed to lowspeed to stop said inotor. l

Q. ln a cont-rol system tor an induction,l inotor, the combination witha plurality-ot windings adapted to produce different speeds in cit-lierdirection, or'.' controller adapted to connect said windings in circuit9i;l in either direction in successive order from low to high speed forstarting said nieto;` f and to cut said. windings out of circuit in thereverse order for .stopping said motoria :ind iueans carried bysaidcontroller fori carrying it past its oti1 position in cutting ontthe windings to normally -connect the low speed winding for the oppositedirection of rotation to cause said windings to exert a braking torce tostop the nictor.

El. ln :i control system for an alternating current inotor` thccombination with a phirzilitv of windings adapted to produceretatiiiginagnetii fields of different speeds, of :i controller for ciittin ot acircuit in suce e oi'dcnt'ronx high speed to low speed to cans saidwindings to exert. a braking eltiort on said rotor, and means adapted tocanse .said controller to automatically reverse the low speed windllfing` atte' :ill ot the windings have been cut out.' 'i

ln Awitness whereof, fl. hereunto subscribe iny naine this 15th dayotApril, A. D.. 1907'.

' Y R. E, NELLE-i UN D.

ico

' lVitncsscs:

Gnonon E. Fenu, ALFnnD H. MOORE.

said windings out

